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Shell_cmd

2018-03-10
layout: post title: “shell cmd” categories: tools

tags: shell
- tags: shell
  - shell命令格式化显示json文件
  - bash脚本中set命令
shell命令格式化显示json文件
```
cat config.json |python -mjson.tool
```
bash脚本中set命令
- set -e Exit immediately if a command exits with a non-zero status 设置了set -e 后的代码，一旦检测到有命令的返回为非零值，则脚本退出
- set -u Treat unset variables as an error when substituting 脚本在替换变量时，如果遇到未定义的变量，则失败
help set
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vim markdown插件

2017-12-17

tools

vim

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Ubuntu常用总结

2017-12-17

tools

vim

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vim使用

2017-11-28

tools

vim

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Linux Kernel initcall机制

2016-10-08

initcall

kernel

相关的文件
相关宏定义
链接生成linux内核文件
内核执行initcalls系列函数

相关宏定义

相关代码如下:

/*
 * Used for initialization calls..
 */
typedef int (*initcall_t)(void);

/* initcalls are now grouped by functionality into separate 
 * subsections. Ordering inside the subsections is determined
 * by link order. 
 * For backwards compatibility, initcall() puts the call in 
 * the device init subsection.
 *
 * The `id' arg to __define_initcall() is needed so that multiple initcalls
 * can point at the same handler without causing duplicate-symbol build errors.
 */

#define __define_initcall(fn, id) \
  static initcall_t __initcall_##fn##id __used \
  __attribute__((__section__(".initcall" #id ".init"))) = fn; \
  LTO_REFERENCE_INITCALL(__initcall_##fn##id)

/*
 * Early initcalls run before initializing SMP.
 *
 * Only for built-in code, not modules.
 */
 #define early_initcall(fn)          __define_initcall(fn, early)

/*
 * A "pure" initcall has no dependencies on anything else, and purely
 * initializes variables that couldn't be statically initialized.
 *
 * This only exists for built-in code, not for modules.
 * Keep main.c:initcall_level_names[] in sync.
 */
#define pure_initcall(fn)           __define_initcall(fn, 0)

#define core_initcall(fn)           __define_initcall(fn, 1)
#define core_initcall_sync(fn)            __define_initcall(fn, 1s)
#define postcore_initcall(fn)       __define_initcall(fn, 2)
#define postcore_initcall_sync(fn)  __define_initcall(fn, 2s)
#define arch_initcall(fn)           __define_initcall(fn, 3)
#define arch_initcall_sync(fn)            __define_initcall(fn, 3s)
#define subsys_initcall(fn)         __define_initcall(fn, 4)
#define subsys_initcall_sync(fn)    __define_initcall(fn, 4s)
#define fs_initcall(fn)             __define_initcall(fn, 5)
#define fs_initcall_sync(fn)        __define_initcall(fn, 5s)
#define rootfs_initcall(fn)         __define_initcall(fn, rootfs)
#define device_initcall(fn)         __define_initcall(fn, 6)
#define device_initcall_sync(fn)    __define_initcall(fn, 6s)
#define late_initcall(fn)           __define_initcall(fn, 7)
#define late_initcall_sync(fn)            __define_initcall(fn, 7s)

#define __initcall(fn) device_initcall(fn)

workqueue.c中

early_initcall(init_workqueues);

扩展开来就是

static initcall_t __initcall_init_workqueuesearly __used\
    __attribute__((__section__(".initcallearly.init"))) = init_workqueues; \

__initcall_init_workqueuesearly 是一个函数指针，指向init_workqueues; 该变量被链接到名为 .initcallearly.init 的 section 中。

linux内核的initcall是分等级的，从init.h中可以看到一共分为17个等级(实际上后接sync的的7个等级是没有用到的)。优先级从上到下越来越低(early > 0 > 1 > 1s > … > 7s)。

链接生成linux内核文件

vmlinux.lds.S是x86内核的链接脚本。该脚本中定义了内核文件中各个section的排列方式。

SECTIONS
{
      . = __START_KERNEL;  // __START_KERNEL = 0XFFFFFFFF81000000
      phys_startup_64 = startup_64 - LOAD_OFFSET;

      /* Text and read-only data */
      .text :  AT(ADDR(.text) - LOAD_OFFSET) {
          ......
      } :text = 0x9090

      ......

      X64_ALIGN_DEBUG_RODATA_BEGIN
      RO_DATA(PAGE_SIZE)
      X64_ALIGN_DEBUG_RODATA_END

      /* Data */
      .data : AT(ADDR(.data) - LOAD_OFFSET) {
          ......
      } :data

      ......

      /* Init code and data - will be freed after init */
      . = ALIGN(PAGE_SIZE);
      .init.begin : AT(ADDR(.init.begin) - LOAD_OFFSET) {
          __init_begin = .; /* paired with __init_end */
      }

      INIT_TEXT_SECTION(PAGE_SIZE)

      // initcall的数据段定义在这里
      INIT_DATA_SECTION(16)

      .x86_cpu_dev.init : AT(ADDR(.x86_cpu_dev.init) - LOAD_OFFSET) {
          __x86_cpu_dev_start = .;
          *(.x86_cpu_dev.init)
          __x86_cpu_dev_end = .;
      }

      ......

      /*
       * start address and size of operations which during runtime
       * can be patched with virtualization friendly instructions or
       * baremetal native ones. Think page table operations.
       * Details in paravirt_types.h
       */
      . = ALIGN(8);
      .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) {
          __parainstructions = .;
          *(.parainstructions)
          __parainstructions_end = .;
      }

      /*
       * struct alt_inst entries. From the header (alternative.h):
       * "Alternative instructions for different CPU types or capabilities"
       * Think locking instructions on spinlocks.
       */
      . = ALIGN(8);
      .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
          __alt_instructions = .;
          *(.altinstructions)
          __alt_instructions_end = .;
      }

      /*
       * And here are the replacement instructions. The linker sticks
       * them as binary blobs. The .altinstructions has enough data to
       * get the address and the length of them to patch the kernel safely.
       */
      .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
          *(.altinstr_replacement)
      }

      /*
       * struct iommu_table_entry entries are injected in this section.
       * It is an array of IOMMUs which during run time gets sorted depending
       * on its dependency order. After rootfs_initcall is complete
       * this section can be safely removed.
       */
      .iommu_table : AT(ADDR(.iommu_table) - LOAD_OFFSET) {
          __iommu_table = .;
          *(.iommu_table)
          __iommu_table_end = .;
      }

      . = ALIGN(8);
      .apicdrivers : AT(ADDR(.apicdrivers) - LOAD_OFFSET) {
          __apicdrivers = .;
          *(.apicdrivers);
          __apicdrivers_end = .;
      }

      . = ALIGN(8);
      /*
       * .exit.text is discard at runtime, not link time, to deal with
       *  references from .altinstructions and .eh_frame
       */
      .exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) {
          EXIT_TEXT
      }

      .exit.data : AT(ADDR(.exit.data) - LOAD_OFFSET) {
          EXIT_DATA
      }

  #if !defined(CONFIG_X86_64) || !defined(CONFIG_SMP)
      PERCPU_SECTION(INTERNODE_CACHE_BYTES)
  #endif

      . = ALIGN(PAGE_SIZE);

      /* freed after init ends here */
      .init.end : AT(ADDR(.init.end) - LOAD_OFFSET) {
          __init_end = .;
      }

      /*
       * smp_locks might be freed after init
       * start/end must be page aligned
       */
      . = ALIGN(PAGE_SIZE);
      .smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
          __smp_locks = .;
          *(.smp_locks)
          . = ALIGN(PAGE_SIZE);
          __smp_locks_end = .;
      }

      ......

      /* BSS */
      . = ALIGN(PAGE_SIZE);
      .bss : AT(ADDR(.bss) - LOAD_OFFSET) {
          __bss_start = .;
          *(.bss..page_aligned)
          *(.bss)
          . = ALIGN(PAGE_SIZE);
          __bss_stop = .;
      }

      . = ALIGN(PAGE_SIZE);
      .brk : AT(ADDR(.brk) - LOAD_OFFSET) {
          __brk_base = .;
          . += 64 * 1024;     /* 64k alignment slop space */
          *(.brk_reservation) /* areas brk users have reserved */
          __brk_limit = .;
      }

      _end = .;
      ......
}

其中INIT_DATA_SECTION 宏定义为:

#define INIT_DATA_SECTION(initsetup_align)                    \
  .init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {           \
        INIT_DATA                                 \
        INIT_SETUP(initsetup_align)                     \
        // initcall defines \
        INIT_CALLS                                \
        CON_INITCALL                                    \
        SECURITY_INITCALL                         \
        INIT_RAM_FS                               \
  }

INIT_CALLS 宏定义为:

#define INIT_CALLS_LEVEL(level)                               \
        VMLINUX_SYMBOL(__initcall##level##_start) = .;        \
        *(.initcall##level##.init)                      \
        *(.initcall##level##s.init)                     \

#define INIT_CALLS                                          \
        VMLINUX_SYMBOL(__initcall_start) = .;                 \
        *(.initcallearly.init)                          \
        INIT_CALLS_LEVEL(0)                             \
        INIT_CALLS_LEVEL(1)                             \
        INIT_CALLS_LEVEL(2)                             \
        INIT_CALLS_LEVEL(3)                             \
        INIT_CALLS_LEVEL(4)                             \
        INIT_CALLS_LEVEL(5)                             \
        INIT_CALLS_LEVEL(rootfs)                        \
        INIT_CALLS_LEVEL(6)                             \
        INIT_CALLS_LEVEL(7)                             \
        VMLINUX_SYMBOL(__initcall_end) = .;

从该ld脚本中可以知道

linux内核文件中各个section的起始地址为0XFFFFFFFF81000000
INIT_CALLS定义在.init.data section中
INIT_CALLS的首尾定义分别为: __initcall_start(0xffffffff82082ef8) 和 __initcall_end(0xffffffff820842f0)

通过命令 readelf vmlinux 和 nm vmlinux 可以查看 __initcall_start 、 __initcall_end 和 __initcall_init_workqueuesearly等函数的地址信息

init_workqueue_early_nm

而init_workqueue函数的地址为, 该函数位于 .init.text section中，该section的起始和结束地址分别为: ffffffff81f56000 和 ffffffff81fbbae4。

init_workqueues_nm

内核执行initcalls系列函数

initcalls在内核初始化过程中调用关系如下

initcalls_invoke

do_pre_smp_initcalls 为 initcall_early的调用函数

static void __init do_pre_smp_initcalls(void)
{
    initcall_t *fn;

    for (fn = __initcall_start; fn < __initcall0_start; fn++)
        do_one_initcall(*fn);
}

__initcall_start对应的是initcall在.init.data section中的首地址， __initcall0_start为 level0的initcall在.init.data section中的首地址，这两个地址之间的函数均为 __initcall_xxxearly 类型的initcall函数。

do_initcalls 为 initcall_levels的调用函数

static initcall_t *initcall_levels[] __initdata = {
    __initcall0_start,
    __initcall1_start,
    __initcall2_start,
    __initcall3_start,
    __initcall4_start,
    __initcall5_start,
    __initcall6_start,
    __initcall7_start,
    __initcall_end,
};

static void __init do_initcall_level(int level)
{
    initcall_t *fn;

    strcpy(initcall_command_line, saved_command_line);
    parse_args(initcall_level_names[level],
           initcall_command_line, __start___param,
           __stop___param - __start___param,
           level, level,
           NULL, &repair_env_string);

    for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)
        do_one_initcall(*fn);
}

static void __init do_initcalls(void)
{
    int level;

    for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)
        do_initcall_level(level);
}

这两个函数中都调用了 do_one_initcall(*fn) 函数，其定义如下：

int __init_or_module do_one_initcall(initcall_t fn)
{
    int count = preempt_count();
    int ret;
    char msgbuf[64];

    if (initcall_blacklisted(fn))
        return -EPERM;

    if (initcall_debug)
        ret = do_one_initcall_debug(fn);
    else
        ret = fn();

    msgbuf[0] = 0;

    if (preempt_count() != count) {
        sprintf(msgbuf, "preemption imbalance ");
        preempt_count_set(count);
    }
    if (irqs_disabled()) {
        strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));
        local_irq_enable();
    }
    WARN(msgbuf[0], "initcall %pF returned with %s\n", fn, msgbuf);

    return ret;
}

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Welcome to My Blog!

Shell_cmd

tags: shell

shell命令格式化显示json文件

bash脚本中set命令

vim markdown插件

Ubuntu常用总结

vim使用

Linux Kernel initcall机制

相关的文件

相关宏定义

链接生成linux内核文件

内核执行initcalls系列函数